After experiencing THE most unstable Ubuntu upgrade yet, my external display resolution was basically a sea of Technicolor vomit. The display on my Dell 1564 i3 was fine, but attaching an external VGA monitor resulted in an unusable display of flickering madness. I also figured out why they called the distro Natty Narwhal: because it acts like a beached whale with a spike in its brain! Fucking Natty.

Anyway, this is how I fixed the garbled external display problem:

1) The Easy Way

a – Open System > Administration > System Testing
b – After entering your admin password, click next. You’ll have a list of many items to test.
c – Chose Monitor Tests and Video Tests

Run the tests with your external monitor detached.

When the tests are complete, run them again with the external monitor attached. You may have to position your mouse on the ‘Test” button before you attach the monitor, since the display resolution will still be garbled once the monitor is attached. When you’re ready, click “Test”. When the tests complete, you should have your external display back. If all looks good, you’ll just have to configure your display settings. And that’s it!

2) The Hard Way
a – Open a terminal and type xrandr
b – You’ll see something similar to this:

Choose which display you want to be your primary and form your command like so: xrandr –output VGA1 –primary

Honestly, this isn’t the best method if you want to fix it visually. Running the Monitor Tests from the System Testing menu uses xrandr anyway and should get your second external monitor up and running. Hopefully things will run better in 11.10 Oneiric Ocelot which will be out in October 2011.